1. Field of the Invention
This invention relates to a composite magnetic head slider which is adapted for flying on an air cushion over a moving magnetic media for recording and reproducing information and, more particularly, to a magnetic head slider assembly wherein a slider body has a side surface which extends substantially perpendicular to an air bearing surface and wherein the slider body has bonded thereto on the side surface thereof a magnetic transducing element. The magnetic transducing element is formed of a polycrystaline ferrite material having a transducing gap located adjacent the trailing edge and air bearing surface. In the preferred embodiment, the magnetic transducing element is affixed to the slider body by means of a bonding layer material in a eutectic mixture comprising by weight approximately 80% gold and approximately 20% tin. This bonding layer material may comprise any other metallic alloy with a melting temperature of less than the melting temperature of the gap material.
2. Description of the Prior Art
A magnetic head slider which is adapted for flying on an air cushion over a moving magnetic media for recording and reproducing tracks of information thereon is well known in the art. The primary use of such magnetic head sliders is in rigid disc drive assemblies. In such disc drive assemblies, it is well known to those skilled in the art to utilize techniques such as down-sizing of magnetic head slider assemblies to reduce disc-to-disc spacing in a drive assembly. Also, it is known in the art that decreasing the data track width increases the storage capacity by increasing the number of data tracks of information on a disc. Also, by reducing the inductance of the head, the recording density on a disc, i.e. flux reversals per inch, can be increased, thus increasing the data that may be stored on the disc.
As a result of the demand to reduce the disc-to-disc spacing and the overall dimensions of a disc drive assembly and in order to improve the operating characteristics of magnetic recording heads used in such applications, magnetic recording heads and magnetic head slider assemblies used in rigid rotating disc drives are decreased in physical size. Further, the characteristics of magnetic transducing heads including read/write gaps, track widths, flying heights are being reduced, while overwrite characteristics are being improved.
By utilizing slider bodies having smaller sizes, the smaller sizes permit processing of slider bodies in a wafer structure using technologies similar to those used for manufacturing thin film devices such as, for example, deposited thin film magnetic transducing heads.
This size reduction in the magnetic head slider is generally accomplished by controlling the height, length and width of the slider body combined with the placement of the read/write or magnetic transducing element in a selected position on the slider body.
The above is generally referred to in the art as "down-sizing". In order to achieve the above objectives several magnetic head slider assemblies have developed in the art. The following are typical examples of the state-of-the-art.
U.S. Pat. No. 4,823,216 discloses a monolithic magnetic head slider assembly having "C" shaped core element formed of the same material as a slider body. This is one example of a 100% form factor slider having a height of about 0.034 inches.
Another magnetic head slider known in the art is the composite magnetic head slider assembly. A typical composite magnetic head slider assembly is illustrated as FIG. 1 of the drawing and is labeled as Prior Art. In FIG. 1, a slider body 20 includes a leading edge 24, a trailing edge 28 and an hydrodynamic surface 30. The hydrodynamic surface 30 is positioned adjacent to a moving magnetic media and co-acts with an air cushion formed by the moving media. A pair of spaced, parallel load rails each having an air bearing surface 32 is formed on the hydrodynamic surface 30. In addition, a side surface 22, which is substantially normal to the hydrodynamic surface 30 and the air bearing surface 32, extends between the leading edge 24 and the trailing edge 28.
The trailing edge 28 has a transverse slot 36 formed therein which is substantially perpendicular to the air bearing surface. The slider body 20 includes a top surface 40 and an elongated core receiving slot 42 that is formed in the top surface 40. The elongated core receiving slot 42 extends through the slider body in the area located at the intersection of the side surface 22 and the trailing edge 28. The elongated core receiving slot 42 is adapted to receive a magnetic transducing element or core assembly shown generally as 50. The magnetic transducing element 50 is typically formed of an "I" bar 54 and a "C" bar 56. A coil winding window 58 is formed in the "C" bar 56.
A coil 60 is wound around and encloses the center of the "I" bar 54. The coil 60 is wound through the coil winding window 58 through the transverse slot 36 to form the magnetic transducing element 50. The magnetic transducing element 50 is secured within or potted into the elongated core receiving slot 42 by means of a bonding material 64 such as, for example, glass, epoxy or the like. Thus, the magnetic transducing element 50 is bonded and held rigidly in place in the elongated core receiving slot 42.
The composite magnetic head slider assembly of FIG. 1 is generally referred to as a 100% form factor slider and has dimensions comprising a height (the distance between the air bearing surface on the hydrodynamic surface and the top surface) of 0.034 inches, a length (between the leading edge and the trailing edge) of 0.160 inches and a width (between the two parallel side surfaces) of 0.126 inches.
Typically, a composite magnetic head slider assembly, as is illustrated in FIG. 1, is limited as to the amount of down-sizing that can be achieved using this structure due to several factors. Physically handling individual magnetic transducing elements 50 of 50% form factor and smaller heads becomes difficult, and physically inserting one core at a time into the slider body is very labor intensive as compared to thin-film head manufacturing techniques. Also, as the size of the magnetic transducing element, which is fabricated from ferrite and/or other high permeability magnetic material, is reduced, internal stresses build up in the magnetic transducing element as a result of the reduced structural size of the core element formed by the "I" bar and "C" bar members, the glass bonding material and glass filler material in the core and the bonding or potting material used to hold the core or magnetic transducing element in the elongated core receiving slot. In general, a high residual stress in the magnetic transducer from glass bonding limits the magnetic transducing elements operating characteristics. However, as the sizes of the "I" bar and "C" bar are reduced, the residual stress from the glass is not reduced. Therefore, the performance of the transducer is limited to an even greater extent than that of the full size transducer.
In order to overcome certain disadvantages of composite magnetic head assemblies, illustrated in FIG. 1 and as described above, thin film magnetic head slider assemblies have been developed. Typical of the present thin film magnetic head slider assemblies is a magnetic head slider assembly disclosed in U.S. Pat. No. 4,928,195. FIG. 2 shown herein and labelled as Prior Art is the thin film magnetic head slider assembly shown herein is based on FIG. 1 in U.S. Pat. No. 4,928,195. In FIG. 2 herein, a slider body 70 is formed to have a leading edge 72, a trailing edge 74, a top surface 76 and a hydrodynamic surface 78. The hydrodynamic surface 78 is formed to have a pair of spaced, parallel load rails, shown generally as 80, which extend generally in direction of media movement shown by arrows 82.
The pair of spaced, parallel load rails 80 are of the same widths and have an air bearing surface (ABS) formed thereon which are utilized as the hydrodynamic flying surface for the magnetic head slider assembly.
The trailing edge 74 of the magnetic head slider assembly 70 has deposited thereon thin film magnetic transducers 88 and deposited electrically conductive members 90 which are operatively connected to the thin film magnetic transducers 88.
The thin film magnetic head slider assembly of FIG. 2 is generally referred to as a 70% form factor slider and has the following dimensions: a thickness of 0.024 inches, a length of 0.112 inches and a width of 0.88 inches.
Another known prior art magnetic head slider assembly which is another example of a 70% form factor magnetic head slider assembly is disclosed in Japanese Laid-open Patent Application 61-137288 (A). Japanese Laid-open Patent Application 61-137288 (A) discloses a slider body having a pair of spaced, parallel rails having air bearing surfaces located on the hydrodynamic surface which are adapted to fly on the air cushion formed on the rotating magnetic media. The relationship between respective rails in Japanese Laid-open Patent Application 61-137288 (A) is that the width of the inner peripheral rail is wider than the width of the outer peripheral side and the relationship between the air bearing surfaces is fixed by the size of the respective parts and the value of the acting air pressure. The slider body in Japanese Laid-open Patent Application 61-137288 (A) has the following dimensions: a thickness of about 0.024 inches, a length of about 0.120 inches and a width of about 0.80 inches.
U.S. Pat. No. 4,894,740 discloses a thin film magnetic head slider which has dimensions approximating a 50% form factor magnetic head slider assembly. The magnetic head slider of U.S. Pat. No. 4,894,740 has a three rail design wherein each rail has an air bearing surface.
As noted above, it is clear that the state-of-the-art magnetic head slider assemblies are continually being reduced in size. The results of analysis of reduced sized slider using a finite element air bearing program based on use of a program known as "AIRHEAD" is described in an article entitled The How and Why of Slider Downsizing by Dr. Paul W. Smith, which appeared in the Magnetic Headlines, Special Comdex Edition, October, 1991, page 1 and 4 (the "Smith Reference") .
The Smith Reference used a "mythical" family of disc drives whose key dimensions are as follows: % Mass or Size Relative to 100% Form Factor
______________________________________ % Mass or Size Form Factor Length Width Thickness Relative to 100% ______________________________________ 100% .160" .126" .034" 100% 70% .112" .088" .024" 35% 50% .080" .063" .017" 12% 25% .040" .030" .008" 1.4" 10% .016" .013" .004" 0.12" ______________________________________
The Smith Reference concluded that down-sized sliders also incorporate lower gram loads and, as a result thereof, the vertical stiffness of the bearing is more than adequately compensated by the reduced mass as shown by the slide form factor curves plotted as a function of a normalized stiffness and frequency as shown in the Smith Reference. Also, the Smith Reference concluded that smaller discs also tended to exhibit lower surface acceleration which improves vertical tracking as well.
It is also known in the art to utilize a slider body in combination with a single crystal ferrite material forming the magnetic transducing element wherein the magnetic transducing element is attached to the side surface of the slider body using a glass bond and known glass bonding techniques. The use of glass bonding techniques are well known in the art and are used primarily for joining together the ferrite elements of a magnetic transducing assembly and as a fillet glass for filling a fillet glass region in an "I" bar and "C" bar core assembly.
Glass bonded ferrite recording heads are subject to appreciable thermal stress because of the differences in thermal expansion between glass and ferrite over the temperature range of the glassing cycle. This is due, in part, not only to thermal stresses developed between the glass bonding layer and the ferrite material, but also to the structural configuration arising from magnetic design constraints, such as the need to focus the magnetic flux at the gap (i.e. with an apex). An analysis of the causes of stress in glass bonded ferrite heads are described in a paper entitled Stress Analysis of Glass-Bonded Ferrite Recording Heads by T. Tang which appeared in the IBM J. Res. Develop., May 1974, pages 274 through 278 inclusive (the "Tang Reference"). The stress analysis described in the Tang Reference is particularly applicable to composite magnetic head sliders described hereinbefore.
However, it is not known in the prior art to utilize a production composite magnetic head slider assembly for magnetic head slider assemblies having a form factor of less than 70% for reasons described above.